Experimento #2

EXPERIMENT No. 2 Identification of elements.
Objective.
Students will identify elements belonging to a family by observing the color of the flame in a burner.

Introduction.
Chinese peopleused gunpowder a thousand years before Christ, and Europeans adopted its use in the Middle Ages. More recently, chemists have found that by adding other metallic compounds, more colorful effects couldbe produced. The reason for this phenomenon is that electrons of these metals become excited due to high temperatures and "jump" to higher energy levels. When those excited electrons return to theirground state, they emit a characteristic light, with a characteristic wavelength and color. Some of the compounds that give specific colors appear in the following table:

Results
* Iron is used tocreate a “bengala effect” on the flame.

Questionnaire
1. What element is present in a salt that produces an intense yellow color?
- NaNO3 (sodium nitrate)
2. Did you see a difference in colorwhen the salt containing barium and the salt containing copper were used?
- When BaSO4 (barium sulfate) was used, the flame turn to a green color, and when CuSO4 (cupric sulfate) was used, theflame turned into yellow but with green also.

3. A sample is suspected to have K, Cs or Na. When put over the flame, the sample produces a violet color. Which element is present?
- KNO3 (potassiumnitrate)

4. Why do colors appear when a substance is put over the flame? Explain in terms of excitation of electrons and quanta of light.
- When a substance gets in touch with a flame, thesubstance’s electrons beging to excite(move) so, when the substance gets in touch with the flame, the flame changes its color because light is absorbed and emitted one photon at a time (a photon is a quantaof light).

5. What element is used frequently in the street lamps?
- Sodium, Neon and Argon.

6. What wavelength (in nanometers) does that light have?
- Sodium light has 589 nm...